Rubbery polymers stabilized with metal salts of alpha, alpha-bis (2-hydroxy-3:5-dialkyl-phenyl) alkanes



illustrate, but do not limit the invention: k

llnited States l atent RUBBERY POLYMERS STABILIZED WITH METAL SALTS F -HY RQX.- =5.,-DI LKYL- PHENYL) ALKANES Harry Edward Jackson, Boris N. Leyland, and John Francis Wood, Blackley, Manchester, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application July 3, 1952, Serial No. 297,182

Claims priority, application Great Britain .iuly 16, 1951 8 Claims. (Cl. 260-810) This invention relates to a new process for preventing the deterioration by oxidation of natural and synthetic rubbers, both before and after vulcanisation.

According to this process, there is incorporated into the natural or synthetic rubber at any suitable stage before curing, a member of a new class of antioxidants, namely normal and basic aluminium, barium, calcium, magnesium, strontium and zinc salts of aa-bis-(2-hydroxy- 3:5-dialkylphenyl) alkanes.

These salts are for the most part, themselves new chemical compounds. They may be made by the condensation of appropriate 2:4-dialkyl-phenols and saturated aliphatic aldehydes in the presence of acid condensing agents, followed by the conversion of the resulting aa-bis-(2-hydroxy-3:S-dialkylphenyl) alkanes to the normal and basic salts of the above mentioned metals. Some of the condensation products are known and the corresponding metal salts can be obtained from these known products.

We have found that these antioxidants not only have excellent preservative properties in rubber and produce little or no staining, but they have excellent physical properties also and are in many cases better adapted for use in the mechanical operations employed in rubber manufacture than are other non-staining antioxidants. They are well adapted for addition to latices of both natural and synthetic rubber.

As particular salts we mention those of the following compounds:

bis-(2-hydroxy-3 :5 -dimethylphenyl) methane bis-(2-hydroxy-S-methyl-3-tert.-buty1phenyl)methane bis-(2-hydroxy-5-methyl-3-tert.-amylphenyl)methane aa-bis-( 2-hydroxy-3 5 -dimethylphenyl) ethane cwz-biS-( 2-hydroxy-3 :5-dimethylphenyl)propane ococ-biS-(Z-hYdIOXY-3 S-dimethylphenyl) butane owt-biS- (2-hydroxy-3 :S-dimethylphenyl) isobutane aa-bis- (2-hydroxy-3 :S-dimethylphenyl) heptane aa-bis-(2-hydroxy-5-methyl-3-octylphenyl)butane aa-bis-(2-hydroxy-5-methy1-3-tert.-butylpheny1)butane ozoc-biS-( 2-hydroxy-3 :S-dioctylphenyl) butane owL-biS-( 2-hydroxy-3 :S-dimethylphenyl) nonane aa-bis-(2-hydroxy-3-methyl-5-ethylphenyl)nonane' owt-biS-( 2-hydroxy-3 S-dimethylphenyl) octane aa-bis-(2-hydroxy-3 5 -dimethylphenyl) dodecane aa-bis-(2-hydroxy 3:5 dimethylphenyuae trimethylhexane A Salts of condensation products of aldehydes with mixed dialkylphenols at least one of which is a 2:4-dialkylphenol may also be employed, e. g. mixtures of such dialkylphenols obtainable from coal tar and especially mixtures containing large proportions of 2:4-.dimethylphenol.

The following examples in which parts are by weight Too 2 EXAMPLE 1 A'solution was made of 5 parts of anhydrous zinc chloride and l part of ammonium chloride in 50 parts of water and the solution heated to 70 C. Meanwhile, 9.9 parts of aza-bis-(2-hydroxy-3:5-dimethylphenyl)butane (M. P. 124l25 C., made by reacting 2:4-dimethylphenol with n-butyraldehyde in the presence of hydrochloric acid) were dissolved in a solution of 2.8 parts of sodium hydroxide in 60 parts of water by heating to 70 C. These two solutions were then added simultaneously over about 5 minutes to 70 parts of water at 70 C. with very good agitation. Agitation was continued for a short time after mixing was completed and the whiteprecipitate was then filtered off and washed with water until the filtrate was chloride free (no turbidity with silver nitrate solution acidified with nitric acid). The product was dried at 50 C. to constant weight. It was a white, freeflowing powder which did not melt below 250 C. and had a zinc content of 19.3%.

In a similar way there were obtained the zinc salts of a a-bis- (2-hydroxy-3 :S-dimethylphenyl) propane, a a-bis- (2-hydroxy-3 :5 -dimethylphenyl) isobutane, and bis-(2-hydroxy-3-tert.butyl-5-methylphenyl)methane. In each case the requisite aa-bis-(2-hydroxy-3:5-dialkylphenyl)alkane was first obtained by condensing the appropriate phenol and aldehyde in the presence of hydrochloric acid as catalyst.

EXAMPLE 2 (a) Preparation of phenol/ aldehyde condensate 61 parts of a phenolic fraction consisting essentially of a mixture of 2:4- and 2:5-dimethylphenols in the approximate proportions of 2:1 were charged to a reaction vessel, 11.3 parts of 35.4% hydrochloric acid added, the mixture stirred and cooled to below 20 C., then 20 parts of nbutyraldehyde run in over about 15 minutes keeping below 30 C. The mixture was then heated with stirring for 3 hours at -105 C., then washed with water (400 parts), secondly with 400 parts of water containing sufficient sodium carbonate in solution to bring the reaction mixture to pH 7, and finally with a further 400 parts of water. After separating the product from the aqueous phase as completely as possible, it was subjected to steam distillation in vacuo using steam at about 100 C. and heating to about C. the pressure being reduced to 100 mm." of mercury; this was continued until 250 parts of distillate had collected in the receiver. The steam was then discontinued and the residue heated a further 15 minutes at 130 C. at 100 mm. pressure to dry it. The product was brown in colour (66 parts by weight) having a melting point (by the steel disc method) of 48 C.

(b) Preparation of zinc salt A solution was made of 298 parts of the product made as above in 1500 parts of water containing 247 parts of 37.5% aqueous sodium hydroxide solution. This solution was heated to 75-80 C. A solution was also made up, and heated to 75-80 C. of 177 parts of anhydrous zinc chloride and 41 parts'of ammonium chloride (to suppress hydrolysis of the zinc chloride) in 1500 parts of 'water. With good agitation, these two solutions were then added simultaneously to 1500 parts of water, keeping the zinc chloride solution slightly in advance of the other solution. After mixing agitation was continued for about 2 minutes, then allowed to settle and the granular solid washed several times with water until essentially free from chloride ions. It was then filtered, washed well with water on the nutsche and dried at 50 C. in an oven. The product was a light fawn powder of zinc content l9.3-l9.5%.

EXAMPLE 3 Vulcanisable rubber compositions were made up by the conventional means according to the following formulae in which the parts are by weight:

Mix A B O The mixes were vulcanised for 30 minutes at 141 C.

Ring-shaped test pieces were cut in the usual way and tensile strengths determined on a Schopper tensile testing machine. Test pieces cut from the same stocks were aged for difierent periods in the Bierer-Davis oxygen bomb under 300 lb./sq. in. oxygen pressure at 70 C. Other test pieces were aged in the Geer oven at 100 C. The tensile strengths of all these test pieces were determined. The results obtained are given in the following table: the unaged figures are actual values obtained in kg./ sq. cm. whilst the aged figures are calculated as per- Vulcanisable rubber compositions were made up by the conventional means according to the following formulae in which the parts are by weight:

Mix

Pale crepe rubber Zinc oxide Blane Fixe. Steario acid. Sulphur Diphenylguanidm e l Zinc salt of phenol/aldehyde condensate made as in Example 2 The mixes were vulcanised for 75 minutes at 141 C., then tested for tensile strength both aged and unaged as in Example 3. In addition test pieces were aged in the Geer oven at 70 C. The results obtained are given in the following table: the unaged figures are actual values obtained in kg./ sq. cm. whilst the aged figures are calculated as percentage retained tensile strengths.

Mix No G H Unaged 204 204 Aged 8 days in bomb Perlshed. 36 Aged 12 days in bomb do 22 Aged 16 days in bomb 23 Aged 2 weeks in oven at 70 71 Aged 4 weeks in oven at 70 C 46 Aged 6 Weeks in oven at 70 C 19 Aged 1 day in oven at 100 0.. 63 70 Aged 2 days in oven at 100 C. 25 27 Aged 3 days in oven at 100 C 6 9 EXAMPLE 5 Vulcanisable rubber compositions were made up by the conventional means according to the following formulae in which the parts are by weight:

Mix I Pale crepe rubber Zinc oxide Blane Fixe Stearic acid Titanium dioxidep Zinc diethyldithioearbamate Zine salt of phenol/aldehyde condensate ma e as in Example 2 The mixes were vulcanised for 12 minutes at C., then tensile strengths of ring-shaped test pieces determined both before ageing and after ageing in the Bierer- Davis oxygen bomb and in the Geer oven. The results obtained are given in the following tables. Unaged tensile strengths are actual figures obtained in kg./sq. cm. whilst aged figures are given as percentage retained tensile strengths:

EXAMPLE 6 A solution was made of 240 parts of the phenol/aldehyde condensate, made as in Example 2 (a) above, in 1200 parts of water containing 200 parts of 32% aqueous sodium hydroxide dissolved therein. A separate solution was made of 248 parts of magnesium sulphate crystals in 1200 parts of water. These two solutions were then simultaneously added, over minutes at room temperature, to 1200 parts of Water containing 14.6 parts of a 20% dispersion of paraffin wax using good agitation. The addition of the magnesium sulphate solution was maintained slightly in advance of the other solution. After mixing agitation was continued for a further 45 minutes then the solid filtered ofi, well washed and dried in an oven at 40 C. The product contained 7.2% magnesium.

Vulcanisable rubber compositions were made up by the conventional means according to the following formulae in which parts are by weight:

The mixes were vulcanised for 75 minutes at 141 C. and tested as in the previous examples with the following results (the unaged tensile figures are absolute in kg/sq. cm.; aged results are expressed as percentage retained tensile strengths): 1

pressed aspbefore). Staini ng was also examined by; the exposure to an ultraviolet lamp and outdoors.

Mix N0 L M 'N' Mix No R S T Unaged 191 174 Unaged 182 165 175. Aged 4 days in oxygen bomb. 68 61 Aged 4 days in oxygen bomb 66 80. Aged 8 days in oxygen bomb 42 '48 Aged 8 days in oxygen bomb Perished. 69. Aged 12 days in oxygen bomb 18 2O Aged 12 days in oxygen bomb d Aged 2 weeks in oven at 70 C 75, 82 Aged 16 days in oxygen bomb 32. Aged 4 weeks in oven at 70 0.. 42 41 10 Aged 2 weeks in oven at 70 C. 41. Aged 6 weeks in oven at 70 C 11 15 17 figgg g 335: 12 gvgg g: Z8 8. 26 V X A A d i d l n t l d 29 35 i ge 8Y8 oven a E MPLE 7 ,Collolllr after 24 hrs. exposure to ultrapale cream cream... cream, Vulcanisable rubber compositions were made up by g i flg aexposure to mm (1) the conventional means according to the followmg for- 15 7 doors. mulae in which the parts are by weight:

1 Very pale cream (fine crazing of surface). 1 Extremely pale cream (a little whiter than R) (no crazlng of surface) O P Q 5 Very pale cream (very fine crazing of surface; better than R).

EXAMPLE 9 Pale crepe rubber 100 100 100 5; g lg lg $2 Vulcamsable rubber compositions were made up by the Stearic acid .1 1 1 1 conventional means according to the following formulae Titanium dioxide. 10 10 10 s n1 phm 5 5 5 in which the parts are by welght. gfl-Nlercaptobenggthiazolge.if iahh a "dung. 0. 5, 0. 5 0. 5 v

ag-nes 11m $3 0 p eno 3| 8 y e 0011 81138- 9 made as in Example 6 1 MIX V W X Zinc salt of phenol/aldehyde condensate made as in l Examp 2 Pale crepe rubber 100 Zinc oxide 10 The mixes were vulcanised for minutes at 141 C., stearic acid f and tested as in the previous examples with the follow- 30 glifiafiilluurm dioxide g Elg/ results (the magedl tenslle figures dare absolute 1n g; i rgiaigl ratt tauata 1 1: 0. 375 g. sq. cm.; age tensl es are expresse as percen age agnes 11111 SE ma 8 as n mp e retained tensile). In addition discs of the vulcamsates Zinc Salt made as in Example 1 were tested for staining properties by exposure under an ultraviolet lamp for 24 hours, and by outdoor exposure for periods of 4 and 6 weeks; the results of these tests are also given below:

Mix No Unaged Aged 4 days in oxygen bomb Aged 8 days in oxygen bomb A ed 112 days in oxygen Aged 20 days in oxygen bomb.

Aged 3 weeks in oven at 70 Agoed 6 weeks in oven at 70 Aged 1 day in oven at 100 0. Agd 2 days in oven at 100 Aged 3 days in oven at 100 Agsd 4 days in oven at 100 Colour after 24 hrs. ex-

posure to ultraviolet lamp.

Colour after 4 weeks outdoor exposure.

Colour after 6 weeks outdoor exposure.

Lt. brown--. Lt. brown.-- Lt. brown.

cream cream very pale fawn. pale fawn.

pale fawn... pale fawn.

EXAMPLE. 8

Vulcanisable rubber compositions were madeup by the conventional means according to the following formulae in which the parts are by weight:

Mix

Pale crepe rubber Zinc oxide Blanc Fixe. Stearic acid Titanium dioxide..." Sulphur Tetramethylthiuram monosulphide 0. Magnesium salt made as in Example 6 Zinc salt made as in Example 2 The mixes were vulcanised for 10 minutes at 141 C. and tested as previously with the following results (ex- The mixes were vulcanised for 12 minutes at 125 C. and tested as previously (results expressed as before). Staining was also examined by exposure to an ultraviolet lamp and outdoors:

Mix No 22 pale fawn.

1 Pale cream (slight crazing of surface). 1 Cream (very fine crazing of surface). 3 Cream (virtually no crazlng of surface).

EXAMPLE 10 A solution was made of 25.6 parts of aza-bis-(Z-hydroxy-3:S-dimethylphenyDmethane (M. P. 144-146" C.) made by reacting 2:4-dimethylphenol with paraform in the presence of hydrochloric acid) in 100 parts of water containing 8 parts of sodium hydroxide. This solution was heated to -70? C. A solution was also made up and heated to 60-70 C. of 20.3 parts of magnesium chloride, MgCl2.6H2O in 50 parts of water. With good agitation these two solutions were then added simultaneously to 25 parts of water at 60--70- C. keeping the magnesium chloride solution slightly in advance of the other solution. After mixing, agitation was continued for 5 minutes and the batch was then filtered. After Washing with water until essentially free from chloride ions the filter cake was dried by heating at C. under a pressure of 20 mm. of mercury. The product was a pale cream powder.

EXAMPLE 11 The calcium salt of bis-(2-hydroxy-3:S-dimethylphenyD- methane was made as described for the magnesium salt in Example 10 but using 15.9 parts of anhydrous calcium 7 acetate in place of the magnesium chloride. The product was a cream powder.

EXAMPLE 12 A solution was made of parts of aa-bis-(Z-hydroxy- 3:5-dimethylphenyl)butane in 100 parts of water containing 2.8 parts of sodium hydroxide. This solution was heated to 7075 C. A solution was also made up and heated to 70-75 C. of 4.8 parts of anhydrous magnesium sulphate in 50 parts of water. With good agitation these two solutions were then added simultaneously to 50 parts of water at 70-75 C., keeping the magnesium sulphate solution slightly in advance of the other solution. After mixing, agitation was continued for 5 minutes and the batch was then filtered. After washing with water until essentially free from sulphate ions, the filter cake was dried at 50 C. in an oven. The product was a pale cream powder of magnesium content 7.4%.

EXAMPLE 13 A solution was made of parts of aa-bis-(2-hydroxy- 3:5-dimethylphenyl)butane in 90 parts of water containing 12.5 parts of 32% aqueous sodium hydroxide solution. This solution was heated to 70 C. A solution was also made up and heated to 70 C. of 10.6 parts of calcium acetate, Ca(C2H3O2)2.I-1zO, in 38 parts of Water. With good agitation these two solutions were then added simultaneously to 25 parts of water at 70 C. Agitation was continued for a short time after mixing was completed and the precipitate was then filtered off, washed with water and dried at 50 C. to constant weight. The product was a light cream powder.

EXAMPLE 14 Using 20.2 parts of aluminium sulphate Al2(SO4)s.9H2O in place of the calcium acetate in Example 13 gave the aluminium salt of aa-bis-(2-hydroxy-3:5-dimethylphenyl)- butane as a pale cream powder.

EXAMPLE 15 A solution of 7.5 parts of aa-bis-(2-hydroxy-3:5-dimethylphenyl)butane in a mixture of 35 parts of toluene and 16 parts of ethanol was boiled under reflux with a solution of 6.65 parts of strontium hydroxide in 100 parts of water with rapid stirring for 3 hours. After filtration, the water, ethanol and toluene were removed by distillation and the residue dried to constant weight at 50 C. The product was a fawn powder.

EXAMPLE 16 Substitution of 8 parts of barium hydroxide Ba(OH)2.8H2O for the strontium hydroxide in Example 15 gives the barium salt of om-bis-(2-hydroxy-3:5-dimethylphenyl)butane as a light fawn powder.

EXAMPLE 17 A mixture of 184 parts of 2-t-amyl-4-methylphenol, B. P. 116-120/ 13 mm. prepared by the reaction of 2- methyl-l-butene with p-cresol in the presence of concentrated sulphuric acid, with 20.25 parts of 37% formalin, 19 parts of hydrochloric acid (86 1.18) and 64 parts of ethanol were boiled under reflux for 4 hours. A solution of 15 parts of sodium carbonate in 150 parts of water was added and the mixture boiled under reflux for /2 hour. The mixture was cooled, 500 parts of water were added and the oil was extracted with ether. The ethereal solution was washed alkali free with water and dried over sodium sulphate. The ether was distilled off and the residue crystallised from aqueous acetic acid giving bis(2-hydroxy-3-t-amyl-5-methylphenyl)methane as colourless needles M. P. 92 93 C.

A solution was made of 15 parts of bis-(2-hydroxy-3- t-amyl-S-methylphenyl)methane, prepared as described above, in a mixture of 40 parts of water and 32 parts of methanol. This solution was heated to 6070 C. A solution was also made up and heated to 6070 C. of 9.1 parts of magnesium chloride, MgCl2.6HzO, in 20 parts of water and 16 parts of methanol. With good agitation these two solutions were added simultaneously to a mixture of 15 parts of water and 12 parts of methanol at 6070 C. keeping the magnesium chloride solution slightly in advance of the other solution. Agitation was continued for 5 minutes and the batch then filtered. The filter cake was washed with 45% aqueous methanol until the washings were substantially free from chloride ion and dried in an oven at 50 C. to constant weight. The product was a pale cream powder.

In a similar way there were obtained the magnesium salts of bis-(2-hydrox -5-methyl-3-t-butylphenyl)methane, aotb1S-(2-h y d r o x y-3 :S-dimethylphenyl) dodecane and ua-bis-(2-hydroxy 3:5 dimethylphenylyyee-trimethylhexane.

EXAMPLE 18 Vulcanisable rubber compositions were made up by the conventional means according to the following formulae in which parts are by Weight:

Mix a b c Pale crepe rubber 100 100 Zinc oxide. 10 10 10 Blane fixe. 75 75 75 Steario acid 1 1 1 Titanium diox1de.. 10 10 10 Sulphur 2 2 2 Zinc dtethyldithlocarbamate 0. 375 0 375 0. 375

Magnesium salt of bis-(2-hydroxy-3z5-dimethylphenyl) methane Calcium salt of bis-(2-hydroxy-3:5-demetl1ylphenyl) methane The mixes were vulcanised for 12 minutes at C. and tensile strength of ring-shaped test pieces determined before and after ageing in the Bierer-Davies oxygen bomb and the Geer oven. Discs of the vulcanisates were tested for staining properties by exposure under an ultraviolet lamp for 8 and 16 hours. The results are given in the following table:

Vulcanisable rubber compositions were made up by the conventional means according to the following for mulae in which parts are by weight:

Mix a e Pale crepe rubber Zinc oxide Blanc fixe Stearic acid..

phenyl) methane Calcium salt of b1s-(2-hydroxy-3:5-dimethylphenly)methane The mixes were vulcanised for 75 minutes at 141 C.

and aged as in the previous example with the followin result (the figures are tensile strengths in kg./ sq. -cm.).

Mix d e f Mix 'n. o p q r Unaged 200 179 8 Unaged 190 198 183 192 173 Aged 3 y in bomb at 70 C. Perisbed 111 110 Aged 8 days bomb at 70 C Perlshed" 88 97 64 75 Aged 2 weeks in oven at 70 C 89 8 8 Aged 12 days bomb at 70 0..... ..do 49 55 25 28 Aged 2 weeks oven at 70 0-- EXAMPLE 20 EXAMPLE 22 Vulcanisable rubber compos1t1ons were made up by the conventional means according to the following forvulcamsalqle er compositlons were made up by mulae in which parts are by weight: the conventional means according to the following formulae in which parts are by weight: Mil 0 h 1 k l 7" Mix 8 t u U w Pale crepe rubber 100 100 100 100 100 100 Zine oxide"-.. 10 10 10 10 10 10 Egg 35g; rubber 198 3. 93 3315110 75 75 75 75 75 75 Blane fixeIII '15 75 15 75 75 steam acid-M 1 1 1 1 1 1 Stearlo acid 1 1 1 i 1 Titanium dioxide 10 1o 1o 10 1o 10 Titanium dioxide 10 1o 10 10 1o Sulphur 2 2 2 2 2 2 Sul hun-.--- IIIIIIIIIII 2 2 2 2 2 Zinc diethyldlthiocarba' Zinc dietbyldithlocarbamate 0.375 0.315 0. 375 0. 375 0.315

mate 0. 375 0- 375 0. 375 U- 375 0- 375 0- 375 Magnesium t of b h Magnesmm Salt of f 3-1:-butyl-B-methylphenyDme i jn 1 l il l ib i n 1 than 1 6 Y p u we Magnesium salt of bIs-(Q-hydroxy- Calcium salt ofaa-biS-(Z- 25 g b 1 gimtmimyl 5 methylphenyDme 1 P i Mameslum salt of aa-biS-(2-hy- Strontium salt of owz-blS- 13 lgig E 5 dime thy1 1 gggigii.5-dimethylphenyl)do- 1 11 1 Ma nesiiii'n'ii'iiiY lSis ii liifi g fi i g gf droxy-3: 5-dimethylphenyl) ye:-

phenynbutane 1 trimethylhexane 1 Aluminium salt of ozoi-biS- g g ggggg 1 The mixes were vulcanised for 12 minutes at 125 C.

"""""""""""""""""""""""" and tested as 'in the previous examples with the following results (the figures are tensile strengths in The mixes were vulcanised for 12 minutes at 125 C. kg./sq..cm.): 'f

Mix s t u v w Urinald 197 Aged 12 days bomb at 70 C Perished.. Aged 16 days bomb at 70 C o Aged 3 weeks oven at 70 C Aged 6 weeks oven at 70 C 29 Aged 32 hours oven at 100 C 71 97 88 Colour after 24 hours exposure to Cream Cream Cream Oream Cream ultraviolet lamp.

and tested as in the previous examples with the following EXAMPLE 23 results (the figures are tensile strengths in kg./sq. cm.):

Vulcanisable rubber compositions were made up by Mix a h i k l m Unaued 212 162 171 151 167 176. Aged 12 days bomb at 70 C Perished 135 1 117 117 132. Aged 16 days bomb at 70 0.- do 107 1 90 Aged3weeks oven at 70 C 100 116 108 116 118 102. Aged 6 weeks oven at 70 C 63. 7 7 7 65. Aged 32 hours oven at 100 C 72 DR 103 111 Colour after 24 hours exposure to Cream Cream Cream.. Crea1n Cream. Cream.

ultraviolet lamp.

EXAMPLE 21 the conventional means according to the following for- Vulcanisable rubber compositions were made up by mulae in which Parts are y Weight! the conventional means according to the following formulae in which parts are by weight:

Mix a: u 2 Mix n 0 p q r Pale crepe rubber 100 100 100 Pale crepe rubber 100 100 100 100 100 Zinc oxide 10 10 10 Zinc oxide 10 10 10 10 10 Blane fixe 75 75 75 Blane fixe 75 75 75 75 75 Stearic acid 1 1 1 Stearic acid l 1 1 1 1 Sulphur 3 3 3 Sulphur 3 3 3 3 3 Dlphenylguanidine .6 0. 5 0.5 Diphenylguauldiue 0.5 0.5 0.5 0.5 0.5 Magnesium salt of bis-(2-hydroxy-3- Magnesium salt of aa-bl -(2-hyd1'0Xymethylpbenyhrnethane 1 3:5-d1methylphenyl) butane 1 Magnesium salt of bis-(2-hydroxy- -t-amyl-5- Calcium salt of aa-bis-(2-hyd1'0xymethylphenybmethan 1 3:5-dimethylphenyl) butane 1 Strontium salt of aa-bis-(2-hydroxy- 3 :5 d1methyl-phenyl1 butane 1 Bariuga sialltl h mfi-tgis-2-hydroxy- 1 3:5- ime yp eny u one Aluminium salt of mz-blS-(2-hyd1OXy- The mixes were vulcanised for minutes at 141 C. sifi'd'methylphenw butane and tested as in the previous examples with the follow ing results (the figures are tensile strengths in kg./sq. cm.):

Mix x y z Unaged 189 187 Aged 8 days bomb at 70 C..." 135 118 Aged 12 days bomb at 70 C 127 123 Aged 16 days bomb at 70 G 84 79 Aged 2 weeks oven at 70 C 186 176 Aged 4 Weeks oven at 70 C. 131 121 Aged 32 hours oven at 100 C 142 11) EXAMPLE 24 1 part by weight of the magnesium salt of phenolaldehyde condensate made as in Example 6 was incorporated by the conventional means into 100 parts by weight of gutta percha. Samples with, and Without antioxidant were exposed to outdoor ageing and time in days noted for them to reach embrittlement:

Days Gutta percha containing no antioxidant 1 Gutta percha containing 1% of above antioxidant--- 9 EXAMPLE 25 Vulcanisable neoprene compositions were made up by the conventional means according to the following formulae, in which parts are by weight:

The mixes were vulcanised for 30 minutes at 152 C. and tested as in the previous examples with the following results (the unaged tensile figures as well as the results after ageing are expressed in kg./ sq. cm.):

Mix Nos I II Unaged. 125 125 Aged 4 days in oxygen bomb 34 99 Aged 8 days in oxygen bomb. 1 24 85 Aged 6 months out of doors 87 95 Aged 1 year out of doors 78 94 Aged 2 years out of doors 49 80 What we claim is:

1. A process for preventing the deterioration by oxidation of a rubber selected from the group consisting of natural and synthetic rubbers obtained by polymerizing a di-olefinic compound before and after vulcanization which comprises incorporating into said rubber prior to curing a material selected from the group consisting of normal and basic aluminum, barium, calcium, magnesium, strontium and zinc salts of cea-blS-(Z-hYdIOXY- 3 5 -dialkyl-phenyl) alkanes.

2. A process as recited in claim 1 in which the magnesium salt of an aa-bis-(2-hydroxy-3:S-dirnethyl-phenyl) alkane is incorporated into natural rubber.

3. A rubber selected from the group consisting of natural and synthetic rubbers obtained by polymerizing diolefinic compound containing a material selected from the group consisting of the normal and basic aluminum, barium, calcium magnesium, strontium and zinc salts of aa-bis-(2-hydroxy-3:S-dialkyl-phenyl) alkanes.

4. A rubber according to claim 3 wherein said material is the zinc salt of bis-(2-hydroxy-5-methyl-3-tert.- butylphenyl) methane.

5. A rubber according to claim 3 wherein said material is the magnesium salt of bis-(2-hydroxy-5-methyl- 3'-tert.-butylphenyl) methane.

6. A rubber according to claim 3 wherein said material is the magnesium salt of bis-(2-hydroxy-5-methyl- 3-tert.-amylphenyl) methane.

7. A rubber according to claim 3 wherein said material is the calcium salt of bis-(2-hydroxy-3:S-dimethylphenyl) methane.

8. A rubber according to claim 3 wherein said material is the magnesium salt of or,a-bis-(2-hydroxy-3:5- dimethylphenyl) butane.

References Cited in the file of this patent UNITED STATES PATENTS 2,295,985 Baird et a1. Sept. 15, 1942 2,354,013 Gump July 18, 1944 2,538,355 Davis et a1. Jan. 16, 1951 2,647,873 Matthews et a1 Aug. 4, 1953 

1. A PROCESS FOR PREVENTING THE DETERIORATION BY OXIDATION OF A RUBBER SELECTED FROM THE GROUP CONSISTING OF NATURAL AND SYNTHETIC RUBBER OBTAINED BY POLYMERIZING A DIOLEFINIC COMPOUND BEFORE AND AFTER VULCANIZATION WHICH COMPRISES INCORPORATING INTO SAID RUBBER PRIOR OF CURING A MATERIAL SELECTED FROM THE GROUP CONSISTING OF NORMAL AND BASIC ALUMINUM, BARIUM, CALCIUM, MAGNESIUM, STRONTIUM AND ZINC SALTS OF AA-BIS-(2-HYDROXY3:5-DIALKYL-PHENYL) ALKANES. 